Field of the Invention
The present invention pertains to medical devices and systems including the versatile system, method and series of apparatuses for creating and utilizing surgical stents and more specifically to a medical device delivery system and, in certain embodiments, particularly to systems and methods involving percutaneous coronary intervention (PCI), angioplasty and stenting.
Description of the Related Art
Arteriosclerosis, also known as atherosclerosis, is a common human ailment arising from the deposition of fatty-like substances, referred to as atheroma or plaque, on the walls of blood vessels. Such deposits occur both in the peripheral blood vessels that feed limbs of the body and coronary blood vessels that feed the heart. When deposits accumulate in localized regions of the blood vessels, blood flow is restricted and the person's health is at serious risk.
Of particular interest to the present invention are balloon angioplasty catheters having a balloon near its distal end for dilating the stenosed region. The angioplasty balloon catheter is then further advanced through the introducer sheath until the balloon passes beyond the distal end of the sheath and into the open vessel where it is aligned with the stenosed region. When the balloon is exposed to the stenosed region, the balloon is inflated to radially expand the vessel at the stenosed region. One particular drawback with such a treatment procedure is excessive vessel traumatization resulting from advancement and retraction of the balloon catheter within the vessel. Another drawback is that such a procedure usually requires the use of an elaborate angioplasty balloon catheter of the procedure. A further drawback is the time required to exchange catheters, thereby further increasing vessel trauma.
Intravascular balloon catheters, and the like, are often utilized in a wide variety of medical procedures to diagnose and treat vascular abnormalities such as aneurysms, stenotic lesions, intracranial shunts, etc. Such balloon catheters may be used for purposes of dilation, occlusion, flow control or tissue reformation.
Intravascular balloon catheters are typically navigated through the vasculature to the desired treatment site using a guide wire. The guide wire is insertable into the catheter and may be torqued to steer the distal end thereof and thereby direct the catheter into the desired vascular passage. Once in the desired position, the balloon may be inflated to treat the vascular abnormality. Such balloon catheters usually include a guide wire lumen shaft to accommodate the guide wire in addition to a separate inflation lumen shaft for inflating and deflating the balloon.
The provision of a guide wire lumen shaft separate from an inflation lumen dictates a catheter profile that may be too large for accessing relatively narrow vasculature often encountered, for example, in cranial applications. Accordingly, it is desirable to provide a combined guide wire lumen and inflation lumen to reduce the profile of the catheter and thereby enable access to narrow vasculature. Balloon catheters incorporating a combined guide wire lumen and inflation lumenare often referred to as “innerless” or “single lumen” balloon catheters.
A single lumen balloon catheter requires some sort of seal or valve between the guide wire and the catheter distal of the inflatable balloon. The seal is typically provided adjacent the distal end of the balloon and forms a close fit or an interference fit with the guide wire. Because of the close fit or interference fit, some friction between the guide wire and the seal may be encountered.
Due to the friction between the guide wire and the seal, in addition to the friction between the balloon and the vasculature, the balloon may be susceptible to longitudinal collapse. The tendency for longitudinal collapse is exasperated by the balloon structure which is usually formed of a thin flexible material.
To address the potential for longitudinal collapse, a support coil may be provided extending from the proximal end of the balloon to the distal end of the balloon adjacent the seal. The support coil provides column strength to the balloon and reduces the potential for longitudinal collapse.
Although the support coil provides column strength to the balloon, the transition in flexibility from the shaft immediately proximal to the balloon to the support coil within the balloon may be fairly abrupt. The support coil is inherently flexible and the balloon is very flexible since it is formed of a thin pliable material. The shaft, by contrast, is usually less flexible to provide sufficient pushability or ability to generate force to propel the apparatus to the desired destination within the subject's body. The result is an abrupt transition in stiffness from the relatively less flexible distal shaft portion to the relatively more flexible support coil and balloon. An abrupt transition in stiffness may translate into reduced trackability and an increased potential for kinking.